FLUIDIZED BED ELECTRIFICATION

Because of the unavoidable tendency of granular solids to become triboelectrically charged when handled, it is no surprise that electrostatic phenomena are often quite pronounced in fluidized and spouted beds. The vigorous motion of fluidized particles—with constant particle-particle and particle-wall contacts—guarantees that electrical charging will take place. Electrostatic adhesion and cohesion, observed and recorded in the very earliest experimental investigations of fluidization, were immediately identified as experimental nuisances to be overcome. Somewhat later, the hazardous nature of electrostatics came to be appreciated. 

Boland and Geldart reported experiments with glass ballotini in a specially designed two-dimensional bed (Boland and Geldart, 1971). To 

Wall-mounted probes, which measure field rather than electrostatic potential, may seem a better choice than suspended probes, but they suffer from the serious problem that charged fines often adhere tenaciously to the sensing electrodes and other surfaces of probes. These charged particles will shield the sensing electrode from the field within the bed and interfere with the measurements. Probably for this reason, very few attempts to use wall-mounted probes are found in the literature. 

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